Mujitsu and Tairaku's Shakuhachi BBQ

How much should the top hole be covered by lower lip?

Im looking into this to correct slightly flat Ri and I - here covering of top hole will
show up any flatness very quickly but also about covering 25% rather than 45-50%
makes a tonal difference as well as pitch.

Be interested in anyone's thought's on this for teaching and my own playing.

direct reply ranft AT ranft.id.au but I will check in here as well.

thanks be happy and well

graham in oz